p53及其靶微小RNA调控前列腺癌细胞竞争骨髓成骨细胞壁龛的研究

The primary cause of the death of prostate cancer (PCa) patients is the bone metastasis of tumor cells. Recent researches revealed that the critical process of bone metastasis of PCa resembled that of hematopoietic stem cells (HSCs), which is so-called "homing" to bone marrow niche that is essentially consisting of osteoblasts. PCa cells competed with HSCs to implant at niche and finally formed bone metastasis. The process of HSCs homing to niche was under the control of p53 that played a key role in the bone metastasis of PCa, and p53-targeted miR-34a mediated the metastatic process. In previous study we found miR-145 repressed the bone metastasis of PCa cells via regulating EMT (PLoS One. 2011;6(5)), and in pretest we discovered miR-145 played important roles in p53-regulating metastasis. Moreover, p53 also suppressed expressions of down-stream factors e.g. CXCR4, but the mechanism of p53 modulating PCa cells competitively binding to osteoblast niche remained unknown. So, in this program we intend to: 1) Identify the influence of p53 at different expression levels imposed on the abilities of PCa cells competitively migrating and adhering to osteoblast in vitro, and competitively homing to osteoblast in vivo. 2) Testify the regulating abilities of miR-34a and miR-145 in the process. 3) Further explore the proteins regulated by p53 and p53-targeted miRNAs and critically functioned in the process of tumor cells competing for niches. Eventually, we want to clarify the mechanism that p53 regulated the bone-metastatic PCa cells competing bone marrow niche, thus providing important basis for studying the prevention and therapy of PCa bone metasis.

最新研究表明前列腺癌（PCa）细胞骨转移关键过程与造血干细胞（HSC）向骨髓成骨细胞壁龛归巢相似，并与HSC竞争该壁龛且定植，但调控这一关键过程的机制还不十分清楚。HSC归巢受p53调控，而我们发现：p53是调控PCa骨转移的重要因素；p53靶微小145通过调节PCa细胞EMT及干性调控骨转移，且在p53调控转移过程中发挥重要作用；p53也了抑制CXCR4等下游效应分子表达。但p53是否是调控PCa细胞与HSC竞争成骨细胞壁龛的关键因素及调控机制仍待阐明。本项目通过观察p53不同水平对PCa细胞向成骨细胞迁移、粘附的能力及竞争性向成骨细胞壁龛归巢能力的影响；验证p53靶微小对其功能的介导作用；并探寻受p53或靶微小RNA调节且在PCa细胞竞争成骨细胞壁龛过程中发挥关键作用的分子，阐明p53对PCa骨转移细胞竞争成骨细胞壁龛的调控作用及机制，为探寻PCa骨转移预防和治疗的新靶标提供重要依据。

前列腺癌（PCa）细胞骨转移关键过程与造血干细胞向骨髓成骨细胞壁龛（niche）归巢相似，并与其竞争该niche且定植。为明确调控这一关键过程的机制，本项目在既往研究的基础上进一步研究发现：1、miR-145介导了野生型p53对前列腺癌细胞的EMT和干细胞特性的抑制作用，从而抑制前列腺癌细胞骨转移的能力。2、ZEB2作为miR-145的靶基因之一，与miR-145通过负反馈机制共同调节前列腺癌细胞的EMT和干细胞特性。这说明p53可以通过调节miR-145的表达来抑制PCa骨转移。我们深入研究后发现：3、WT-p53缺失会上调PCa中CXCR4与N-Cadherin的表达，增强细胞迁移以及粘附至成骨细胞壁龛的能力，这说明N-Cadherin及CXCR4是受p53直接转录调节并在调控肿瘤细胞竞争成骨细胞niche过程中发挥关键作用的分子。同时，使用CXCR4和N-Cadherin拮抗剂处理WT-p53下调的前列腺癌细胞能够明显逆转这一过程。这说明CXCR4及N-Cadherin可能作为前列腺癌骨转移治疗的靶标。4、N-cadherin还可以通过ErbB通路促进前列腺癌细胞的EMT和干细胞特性，从而促进前列腺癌细胞骨转移的能力。这也进一步支持了N-cadherin可能作为前列腺癌治疗的目标分子。5、我们还证实了FZD8也是WT-p53的靶基因之一，其通过激活经典WNT/β-catenin信号通路增强前列腺癌细胞迁移、侵袭能力及肿瘤干细胞特性的作用。临床标本中，WT-p53的表达情况与FZD8和β-catenin的表达呈负相关。这提示FZD8也参与促进前列腺癌进展与骨转移，p53／FZD8／WNT／β-catenin轴可能作为前列腺癌治疗的目标之一。6、除上述机制外，我们还发现miR-100可以负反馈调节AGO2的表达，其表达丢失可以促进前列腺癌细胞骨转移的能力, 提示miR-100/AGO2轴也可能作为前列腺癌治疗的靶标。上述结果大部分已发表在SCI期刊上，总IF 12.002，最高3.018，另有J Pathol修回文章, IF7.38。本项目发现受p53或靶miRNA调节且在PCa细胞竞争成骨细胞壁龛过程中发挥关键作用的分子，阐明了p53对PCa骨转移细胞竞争成骨细胞壁龛的调控作用及机制，为探寻PCa骨转移预防和治疗的新靶标提供了重要依据。